Due to rapid growth in use and applications of digital information technology, there are demands to continuingly increase the memory density of memory devices while maintaining, if not reducing, the size of the devices. Three-dimensional (3D) structures have been investigated for increasing the memory density of a device. For example, 3D cross-point memory cells have been investigated as devices with increased capacity and smaller critical dimensions. These 3D structures include stack structures of memory cells that may include chalcogenide materials, conductive materials, and, optionally, organic materials.
The stack structures are formed from a variety of materials, such as chalcogenide materials, organic (i.e., carbon) materials, or other sensitive materials, that are sensitive to downstream processing conditions. Following the formation of these materials, the materials are etched to form the stack structures. Since the stack structures are formed of many different materials, post-etch residues remaining on the stack structures include a complex mixture of materials. Conventionally, the post-etch residues on the stack structures may be removed by cleaning with compositions that include acetic acid, citric acid, oxalic acid, dilute ammonium hydroxide (NH4OH), hydrogen fluoride (HF), or combinations thereof. However, the variety of materials in the stack structures makes etching, post-etch cleaning, and other downstream processes difficult because no single, conventional composition is useful to remove all residues. In addition, since the stack structures include different chalcogenide materials, there are volatility, solubility, and electrochemical potential differences between the chalcogen elements and metal elements of the chalcogenide materials that need to be balanced. These differences cause cross contamination of the metal elements of the chalcogenide materials during post-etch cleaning with conventional compositions. The conventional compositions are typically solvent-based or acid-based to decrease galvanic corrosion and other damage of the stack structures. For example, metal elements of the chalcogenide materials in the stack structures may migrate from one part of the cell structure to another when contacted with the conventional compositions. In the presence of the solvent-based or acid-based compositions, these metal elements or chalcogen elements may diffuse and form insoluble complexes with other materials of the stack structures, which poisons the memory cells, leads to programming issues, and reduces the electrical performance of a semiconductor structure including the stack structures. In addition, organic materials of the stack structures are damaged by the conventional solvent-based or acid-based compositions. To reduce damage to the different materials of the stack structures, multiple compositions may be used to clean the stack structures. Alternatively, the stack structure may be formed in multiple acts to minimize damage to the stack structures. However, using multiple compositions or multiple processing acts add complexity to the overall fabrication process.